Photographic reversal process



June 10, 1930. w, SEYMQUR 1,762,936

PHOTOGRAPHIC REVERSAL PROCESS Filed Aug. 21, 1928 PI 1.26 25 v 17 18.JECOND DEVELOPING 51111-95 DEVELOPING, BLEA NING mun CLERRING BnTHs Fig553.

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Patented June 10, 1930 UNITED STATES PATENT OFFICE MERRILL W. SEYMOUR,OF ROCHESTER, NEW YORK, ASSIGNOR TO EASTMAN KODAK COMPANY, OF ROCHESTER,NEW YORK, A CORPORATION OF NEW YORK PHOTOGRAPHIG REVERSAL PROCESSApplication filed August 21, 1928. Serial No. 301,068.

produced by a White light exposure may be removed or reduced by exposureto red light and that this action of the red light is accelerated if.the film is bathed in a desensitizing dye before or during the red lightexposure.

It has also been discovered that in a reversal process the sensitivityof the bleached image prior to the second development is lessened by'the application of red light.

I have discovered that these photo chemical reactions may be applied tothe control of the final or second image in a reversal process. Myinvention involves the use of these properties by the exposure of thesensitive bleached film to a source of constant actinic light and to adesensitizing red light controlled in accordance with the printingvalueof the image.

By the term actinic light, as used herein, I mean light of such wavelengths as to render the emulsion developable. It has been found thatthe best results are obtained in the processes herein outlined if thered rays are excluded from actinic light so that instead of being White,it Will be distinctly stated in said Capstafi patent except as hereinnoted and a repetition thereof is unnecessary.

The vital steps of a reversal process are the following: I

(a) First exposure, image printed;

(6) Develop to a silver image;

(0) Bleach, i. e. remove the silver image;

((Z) Clear, i. e. remove undesired products 01" bleaching bath;

(6) Second exposure to printing light; I

(f) Redevelop.

It is of course understood that the other described steps may be andpreferably are used but the above are essential.

I will now describe various typical procedures that illustrate theapplication of my invention.

The film or plate bearing a bleached image may be viewed or measured bya light, either actinic or non-actinic, between steps (0) and As pointedout in the cited patent, it is not sensitive at this time. However thebleached image is present and may be examined. The film or plate is thencleared by the usual process, rendering itilight sensitive, after whichit is submitted to a red or non-actinic light, the intensity or durationof the exposure being varied or controlled to dcsensitize the film orplate by the desired amount. It is then submitted to actinic light ofconstant intensity and duration just sufiicient to furnish the maximumexposure that would be desired,that is, in case of grossover-exposure,when the controlled exposure to red light Would be reducedto zero and sufiicient actinic light would be required to render all theremaining silver salts developable.

A second method is identical with the first except that the film orplate is measured or judged immediately after step (d) instead ofbefore, this examination being by red light, the intensity or durationof which is under the control of the operator who thus uses the same redlight both for the exami nation and the desensitizing of the material.It is then submitted to a constant actinic light and developed.

A third method comprises the exposure after step (d) to actinic light ofconstant intensity and duration suiiicient to render the sensitive saltsfully dcvelopable, after which the film or plate is exposed to a redlight, of which the intensity, duration or both are controlled or variedto destroy partially the latent image produced by the actinic light. Inthis method, the image may be judged or measured by white light prior tostep (d), by a short red light exposure after step (d) and prior to theactinic light exposure, simultaneously with the controlled red lightexposure, or simultaneously with the actinic light exposure.

I have discovered that the latent imagedestroying effect of the thirdmethod is markedly increased by submitting the film or plate to a bathincluding a desensitizing dye prior to both exposures, the other stepsof the method being as above described. The constant actinic lightexposure must in this case be much greater than when this step isomitted, but the differential effect obtained by the red light isgreater.

I also consider as within the scope of my invention the use of such adesensitizing dye in the first and second methods prior to bothexposures to augment the desensitizing effect of the red light.

A known desensitizing dye such as phenosafranine. may be used, having adilution of one part to 3000 parts of water, with 30 parts ofpotassiumbromide by weight. The same effect has been obtained with theother known de-sensitizing dyes, used at customary dilutions.

In carrying out the third method it is possible to use a desensitizingdye and still avoid the heavy exposure to white light by first exposingto a constant actinic light, then bathing in a desensitizing bath, andthen giving a controlled red light exposure. The image is preferablyexamined by the red light, although it may be judged by the actiniclight.

This 1s my preferred process and the vital steps of the completereversal process involving the improved steps at the points when Iconsider them most desirable will be again enumerated.

I. Expose;

II. Develop;

III. Bleach;

IV. Clear;

V. llxpose to constant. aetinie light;

VI. Bathe wi h desensitizing dye;

VII. Expose to controlled red light. at the same time measuring orjudging the image;

VIII. Redevelop;

IX. l" ix out remaining silver salts.

The details of these steps are as in the cited patent or as given in theabove description. All of the accompanying claims cover this preferredmethod and certain of them are specific to it.

It is impossible to give definite light intensities or strength oidensensitizing baths to secure the best results under all circumstances,since this varies widely with the emulsions and the particulars of theprocess as actually carried out. In general it may be stated thatconsiderably more exposure to red light is necessary for instance. thanmere 1 1y passing a film over a small inspect-ion red window. Anappreciable effect is ob ained however with a moderate exposure,particularlyif the iihn has been first submitted to a desensitizing dyebath.

As pointed out in the Capstaff Patent 1,460,703 the judgment ormeasurement of the film may be an inspection dependent on the skill andexperience of the operator, an instrumental comparison, or a developingtest. I

It is also possible to vary both the actinic light and the non-actiniclight, the respective exposures being such as to produce a finaldevelopable image as required by the ascertained printingcharacteristics of the film.

Comparing this method with that of the Capstatt Patent 1,460,703, itmight be said that in that patent a certain minimum second exposure isgiven such as would be necessary for an original gross umlerexposure,and to this is added an exposure as required by the printingcharm-toristirs of the tihn up to a maximum which would be required fora gross over-exposure: while in the present process, there is given amaximum exposure such as would be required for an original grossoverexposure and from this is subtracted, by reducing the developableaction by a controlled amount, an exposure as determined by the printingvalue of the image.

It is obvious that any of the processes including my invention can beperformed without special apparatus other than would be used forcustomary photographic operations and that in treating motion picturefilm continuously as in machines of the type shown in the patent of J.G. Capstatt 1,690,616, granted Nov. 6, 1928, or the British patent ofKodak Limited 297,995, accepted October 4, 1928, modifications couldreadily be made to adapt them to our process.

As an illustration of how such an adapta tion may be made, reference ismade to the accompanying drawing, in which Fig. 1 is a diagrammaticshowing of part of a continuous processing machine adapted for thecarrying out of my process, and Fig. 2 is a similar showing of such a.machine for automatically controlling the red light.

Only certain elements of the apparatus are ion indicateddiagrammatically, the complete machine being fully disclosed in thepatent-s referred to above and not constituting my invention.

A continuous film F emerges from a tank or tube 1 which is one of aseries of tubes through which it has been drawn in the processingoperation. At this stage it has been developed, bleached, and clearedand is a film band carrying a layer containing a positive image ofunexposed sensitive silver salts. The film passes over a sprocket 2, andguide rolls 3, the latter holding it submerged in a tray 4, containingwater and having a transarent bottom 5 beneath which is a lamp 6 1n lamphouse 7. In use this lamp furnishes an even illumination and as the filmmoves at a constant speed the exposure of all points is the same. Thislamp also furnishes light by which the film may be inspected, udged ormeasured. The film then passes over a sprocket 8 through a tube 9containing a desensitizing bath to two sprockets or rolls 10 to a tube11 containing water and thence to other tubes 12 containing baths forthe completion of the reversal process. A lamp box 13 extends along theupper half of the tube 11, which is of glass. This lamp box contains arow of lamps 21 and a weighted shutter 14 sliding in guides 15 t-o'whichis attached a cord 16 passing over a graduated arcuate guide 17 on themain frame 20 of the machine. The cord is attached to a control handle18 pivoted at 19 to the frame 20 and having a latch 25 engagingtheratchet teeth 26. The frame 20 also supports the other describedelements of the machine. The lamp house carries a screen 22 extendingits full length which transmits only red and infra red light. An opaquepartition 24 is placed between the reaches of film in the tube 11 sothat only one reach is exposed to the red light.

In practice the operator judging or measuring the printing value of theimage as it passes the constant light sets the handle 18 at the propertime so that as the film passes the red light the extent of its exposurewill be controlled as required. In each of the figures the arrowindicates the direction of movement of the film.

In Fig. 2 is shown an apparatus embodying the automatic features of theabove mentioned British patent as applied to the carr ing out of myprocess in a continuous machine. The film F passes up from a tube 1 asbefore, over sprocket 2, rolls 3, through tank 4, over the lamp 6 andbeneath a radiation responsive element 30 such as a thermopile. It thenpasses over rolls 50, beneath rolls 51 directing it through a secondtray 52 containing a concentrated desensitizing dye solution, then overroll 53 to rolls 31 which direct the film through tray 32 containingwater, thence to the second sprocket 45, and to processing tubes 12.Above the tray 32 is a lamp house 33 containing a powerful light source34 rich in red light, with a reflector 35 and condensing lenses 36.Between the condenser lenses is a fixed opaque diaphragm plate 37 havingan opening 38 and across this moves an opaque .vane 39 pivoted at 40 andcontrolled by a alvanometer or millivoltmeter 41 connecte by wires .42to the thermopile 30. At the bottom of the lamp house is a filter 43transmitting only red and infra red light. This instrument is describedin detail in said above mentioned British patent.

As the film passes beneaththe thermopile the latter is controlled tooperate the vane to cover or uncover the diaphragm opening more or less.

It is obvious, Without further explanation, how'the apparatus is used inthe carrying out of the invention and that analogous apparatus can bedesigned for carrying out other modifications of my processcontinuously.

I contemplate as within my invention all such modifications andequivalents as fall within the scope of the appended claims.

Having thus described my invention, What I claim as new and desire tosecure by Letters Patent is:

1. In a process of making photographic images by reversal from aphotographic element containing an image and containing light sensitivesalts, the steps of giving said element an exposure to an actiniclightand an exposure to a non-actinic light capable of lessening theeffect of the exposure to actinic light, the last named-exposure beingcontrolled in accordance with the acteristics of the element. I

2. a In a process of making photographic images by reversal in asensitive photographic element containing an image, the steps ofdetermining the printing characteristics of said image, submitting theelement to a standard exposure to an actinic light, and to an exposureto a non-actinic light capable of lessening the effect of the exposureto actiniclight, the extent of the last named exposure being controlledin accordance with the ascertained characteristics of the image, anddeveloping an image in said element.

3. In a process of making photographic images by reversal from aphotographic element containing an image and containing light sensitivesalts, the steps of exposing said element to. an actinic light, theexposure having a fixed standard value independent of the image, and toa red light the extent of the exposure to the red light being controlledin accordance with the printing value of the element and developing animage in said element.

4. In a process of making photographic positive images by reversal fromphotoprinting charv I graphic negative silver images in an emulsioncontaining light sensitive salts, the steps of removing the silver fromthe emulsion, (lotermining the printing characteristics of the emulsion,submitting it to an actinic light and to a non-actinic light capable oflessening the effect of the actinic light, the exposure to the lastnamed light being controlled in accordance with the ascertained printingcharacteristics and developing an image in the emulsion.

5. In a process of making photographic images by reversal from aphotographic negative image in a light sensitive element, which processcomprises rendering the negative image inert and differentiallytransparent, then exposing to actinic light, and then developing thesensitive image, the step after such rendering and prior to developingof submitting the element to a red light, the extent of the exposure tored light being controlled in accordance with the printing value of theelement.

6. In a' process of making photo aphic images by reversal from photograpic images in a light sensitive element, the steps of measuring theprinting characteristics of the element, giving the element a standardexposure to actinic light, and exposing the element to a red light, theextent of such last named exposure being controlled in accordance withthe ascertained printing characteristics of the film.

7. In a process of making photographic images by reversal from aphotographic element containing an image and containing light sensitivesalts, the steps of giving said element an exposure to an actinic light,and an ex osure to a non-actinic light capable of lessenmg the effect ofthe exposure to actinic light, the last named exposure being controlledin accordance with the rinting characteristics of the element, an priorto the exposure to non-actinic light, submitting the element to a bathhaving the eflect of accelerating the action of the non-actinic light.

8. In a process of making photographic images by reversal in a sensitivephotogra hic element containing an image, the steps 0 determining theprinting characteristics of said image, submitting the element toa'standard exposure to an actinic light and to an exposure to anon-actinic light, capable of lessening the eflect of the exposure toactinic light, the extent of the last named exposure being controlled inaccordance with the ascertained characteristics of the image and, priorto the exposure to non-actinic light, submitting the element to a bathhaving a tendency to desensitize the element to actinic light and toaccelerate the action of thenon-actinic light.

9. In a process of making photographic images by reversal fromphotographic images in a light sensitive element, the steps of measnringthe printing characteristics of the element, giving the element astandard exposure to actinic light, and exposing the element to a redlight, the extent of such last named exposure being controlled inaccordance with the ascertained printing characteristics of the filmand, prior to the exposure to red light, submitting the element to abath containing a desensitizer.

10. In a process of making photographic images by reversal from aphotographic element containing an image and containing light sensitivesalts, the steps of first giving said element a standard exposure to anactinic light and then giving it an exposure to a nonactinic lightcapable of lessening the effect of the actinic light, the extent of thelast named exposure being controlled in accordance with the printingcharacteristics of the element.

11. In a process of making photographic images by reversal from aphotographic element containing an image and sensitive salts, the stepsof giving said element an exposure to an actinic light rendering thesalts developable, and thereafter an exposure to non-actinic lightcapable of reducing the developability of said salts, the secondexposure being controlled in accordance with the printingcharacteristics of the image, and at a point in the process prior tosaid second exposure treating the film to accelerate the effect of saidsecond exposure.

12. In a process of making photographic images by reversal from aphotographic element containing an image and sensitive salts, the stepsof giving said element an exposure to an actinic light rendering thesalts developable, and thereafter an exposure to nonactinic lightcapable of reducing the developability of said salts, the secondexposure being controlled in accordance with the printin characteristicsof the image, and at a point in the process prior to said secondexposure treating the film with a desensitizing dye having the effect ofaccelerating the effect of said second exposure.

13. In a process of making photographic images by reversal from aphotographic element containing an image and sensitive salts, the stepsof giving said element a standard ex osure to an actinic light renderingthe sa ts developable, thereafter submitting the element to a bathnormally having the effect of desensitizing sensitiv e salts to actiniclight, and then exposing the element to a non-actinic light capable ofreducing the developabilitv of the salts, the extent of the lastexposure being controlled in accordance with the printingcharacteristics of the element, and then developing an image in saidelement. L J 14. In a process of making photographic images by reversalfrom a photographic element containing an image and containing lightsensitive salts, the steps of first giving said element an exposure toan actinic light rendering the salts developable and then an exposuretoa non-actinic light capable of reducing the developability of the salts,and

during the process determining the printing characteristics of theimage, the extent of the second exposure being controlled by theascertained printing characteristic.

Signed at Rochester, New York this 10th day of August 1928.

MERRILL W. SEYMOUR.

